Method and device for the automated classification of a liquid as well as method and device for the automated adaption of presettings for a capacitive liquid level measurement

ABSTRACT

A device which has a deliverable sensor, a container for receiving a liquid, a container environment and a signal processing circuit, the input side of which can be connected circuitry-wise to the sensor. The device is designed to perform a capacitive liquid level measurement in normal operation using the sensor, wherein a threshold value can be predefined for the signal processing circuit for normal operation. The device has a classification module which can be connected with an input side or line connection circuitry-wise to the sensor, is designed to make a capacitive measurement of the liquid in the container using the sensor and can be connected circuitry-wise to the signal processing circuit in order to trigger the specification of a threshold value using the sensor for capacitive measurement of the liquid.

RELATED PATENT APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 14/683,863 filed on Apr. 10, 2015, which claims priority on Swisspatent application No. CH 00570/14 filed on Apr. 14, 2014, the wholecontent thereof being incorporated into the present application byexplicit reference for any purpose.

The invention relates to methods for the automated classification of aliquid in a device which is designed to make a capacitive liquid levelmeasurement in a container which is filled with the liquid. Theinvention also relates to corresponding devices.

The invention also relates to methods and devices for the automatedadaptation of presettings for a capacitive liquid level measurement,where preferably the presettings are made by reference to an automatedclassification.

BACKGROUND OF THE INVENTION

There are numerous medical, biological, chemical and pharmaceuticaldevices which involve the handling and use of liquids. Thus, forexample, there are automated handling systems in order to carry outmedical, biological, physical and chemical investigations or to carryout processes in the corresponding technical or scientific fields.

Nowadays, most of the automated liquid handling systems are so-calledcomputer-controlled handling systems.

A typical computer-controlled handling system comprises, for example, awork area (worktable or surface) for the placement of liquid containers,a motorized pipetting robot and a controller (usually a processor-basedcontroller). The pipetting robot comprises at least a pipette foraspirating and dispensing liquid samples. By implementing a sequentialprogram which is executed in the controller, the pipetting robot can bemoved to a specific position in order to execute a specific handlingthere. Thus for example, a pipette can be lowered into a container inorder to suck up a liquid there or to dispense a liquid. Modern handlingsystems typically comprise means which make it possible to determine theliquid level of a liquid in a container of the handling system. Thedetermination of the liquid level is of basic importance for a number ofprocess sequences. For example, if one wished to prevent airaccidentally being sucked in when sucking up liquid, it must bepreviously ensured that the pipette is immersed sufficiently far intothe liquid. In order to accomplish a sufficiently far immersion in anautomated sequence, the instantaneous liquid level of the liquid in thecontainer must be determined.

There are also numerous other examples for sequences in which the liquidlevel of a liquid must be determined.

The liquid level of a liquid in a container can, for example, bedetermined by means of a capacitive liquid level measurement (alsocalled cLLD for capacitive liquid level detection). Since a gas and aliquid have significantly different dielectric constants, the gas-liquidphase boundary can be determined by means of a change in capacitance.

The detection of a phase boundary is typically made in a capacitivemanner, as shown schematically by reference to FIG. 1. FIG. 1 shows thestructure of a known laboratory apparatus 10 which is here designed fordetecting a liquid level. The presence of a liquid 1 in a container 5 orthe phase boundary between air and liquid 1 is here detected, forexample, by observing the capacitive change of C_(tip/liq) and of theseries capacitance C_(coupl). An electronic charging/discharging circuit2 provides for an alternate charging and discharging in order to be ableto measure the effective capacitance between a sensor, e.g. in the formof a pipette tip 3 and an earthed base plate 4. The signal processingcan be accomplished by means of a signal processing circuit 6 which, forexample, is supported by a controller 7.

The effective capacitance, which results, depending on the laboratoryapparatus 10 from the stray capacitances, electrical couplings throughthe sensor or the pipette tip 3, the conductivity of the liquid 1 andthe crosstalk between adjacent measuring channels (referred to as nexttip in FIG. 1) is very small. It is typically in the range of a fewpicofarad (pF). The capacitance change, which results upon plunging fromthe air into a liquid is once again less by approximately a factor of100 to 1000.

Details of a device with capacitive liquid level measurement can beobtained, for example, from one of the published patent applicationsEP2530440A1 and WO2011080199A2 of the present applicant.

In handling systems with capacitive liquid level measurement, the usermust make a basic setting so that the capacitive liquid levelmeasurement can be made reliably and precisely by the system. It is saidthat the correct setting of the detection parameters must be mademanually before a capacitive liquid level measurement can then besuccessfully made.

The setting of the detection parameters depends inter alia on physicalproperties of the liquid for which the liquid level is to be determined.These physical properties of the liquid to be investigated or measuredare however frequently not known or only known in the form of estimatedvalues. It is obvious that an incorrect or inaccurate specification ofthe detection parameters can lead to inaccurate or even incorrectdetection results in the liquid level measurement.

It is now the object to provide a method which enables the automateddetermination and/or the automated setting of the detection parameter(s)in a handling system.

The invention relates in particular to the automated classification of aliquid and/or the application of a capacitive liquid level measurementcLLD by applying a previously made classification of the liquid.

In particular, a method and a device for the automated classification ofliquids are to be provided.

A method and a device for the automated specifications of a setting orfor the setting of a device is to be provided so that a capacitiveliquid level measurement can be successfully carried out. Acorrespondingly equipped device is also to be provided.

According to the invention, a method for the automated classification ofliquids in a device is provided, where the device is also designed tomake a capacitive liquid level measurement in a container which isfilled with a liquid.

The method of the invention comprises the following steps:

-   providing the liquid in a container,-   performing a capacitive measurement of this liquid    -   -   when executing an immersion movement of a sensor into the            liquid in the container or        -   when executing an emerging movement of the sensor out from            the liquid in the container,            where a signal of the capacitive measurement is processed in            order to make the automated classification of the liquid.

Preferably in all embodiments a signal jump of a signal of thecapacitive measurement is processed, where the signal jump is producedduring the immersion movement of the sensor into the liquid or duringthe emerging movement of the sensor out from the liquid. The automatedclassification of the liquid is made by means of an analysis orprocessing of the signal jump.

Preferably in all embodiments a liquid-specific threshold value isdetermined by way of the capacitive measurement of this liquid whenexecuting the immersion movement or the emerging movement, where asignal of the capacitive measurement is processed to determine thethreshold value.

Preferably in all embodiments the threshold value is related to a jumpin the capacitance (signal jump) which occurs during immersion oremergence.

Preferably in all embodiments when determining the threshold value oneor more of the following details or parameters or factors arespecified/predefined/known:

-   -   the type of container (geometry, wall thicknesses, material),    -   the liquid volume of the liquid in the container,    -   the type of sensor (e.g. fixed steel cannula, disposable pipette        tips made of conducting plastic having different nominal        volumes),    -   the type of carrier for the container,    -   the type of worktable on which the carrier is disposed.

According to the invention, an automatic classification or division ofliquids into sensitivity ranges (hereinafter also designated assensitivity classes) is made where this is accomplished by using thecapacitive measurement. In this case, the classification/grouping of theliquid is made in a capacitive manner

-   -   by means of a sensor which can be delivered into a liquid and/or    -   by means of a sensor which can moved out from a liquid.        This classification/grouping of the liquid is made by        determining a liquid-specific value, a liquid-specific series of        discrete values or a value function which is/are related to one        or more predefined threshold values or comparison criteria. The        classification of the liquid into one or more sensitivity        classes or groups is then made by relating to one or more        predefined threshold values or to comparison criteria.

According to the invention, preferably a plurality of signal jumps orintensity values are determined and an average is formed from the signaljumps or the intensity values.

Advantageous embodiments can be deduced from the respective subclaims.

In particular, the invention relates to a method forclassifying/grouping liquids in a device which comprises a capacitivelyoperating measuring device which is designed for the detection of phaseboundaries (here called capacitive liquid level measurement or cLLD forshort).

By using the invention, sensitivity settings can be predefined which aresuitable for making a subsequent capacitive liquid level measurement(cLLD) rapidly and reliably.

Preferably all embodiments are concerned with the automatedspecification of threshold values which are particularly preferablyspecified as adaptive threshold values.

Preferably in all embodiments the threshold values correlate with thepredicted signal intensity during the immersion and/or emergence.

Preferably in all the embodiments the threshold values have a dependenceon the liquid volume which is to be detected by means of cLLD.

Particularly preferably in all the embodiments the threshold values havea dependence on the size of the interface which is obtained between theliquid to be measured and the container, i.e. a dependence on theso-called wetted area.

Preferably in all embodiments the sensitivity setting can be trackedand/or adapted dynamically where this is accomplished particularlypreferably as a function of the wetted area.

Preferably in all embodiments two or three sensitivity groups arepredefined where each of these groups has its own specific sensitivityprofiles as a function of the liquid volume and/or the wetted area.

Particularly preferred are embodiments in which each of the sensitivityclasses has its own specific threshold value profile (adapted to orderived from the sensitivity profile).

The shape (geometry) of the container and the liquid volume to bedetected are also relevant. Therefore preferably in all embodiments thesensitivity is dependent on the shape (geometry) of the container or thewall surface which is covered by the liquid (called wetted area).

The threshold value(s) which has/have been assigned as liquid-specificvalues of a liquid or the classification or grouping of a liquid can beapplied according to the invention, for example, in other systemarrangements or configurations, by for example converting the thresholdvalues or by retrieving corresponding entries from a table or a memoryby means of a table enquiry. This principle can be applied to allembodiments of the invention.

The threshold value(s) which has/have been assigned as liquid-specificvalues of a liquid or the classification or grouping of a liquid can beused in connection with other labware. This principle can be applied toall embodiments of the invention.

In preferred embodiments of the invention, one or more of the followingstatements/rules is implemented:

-   the sensitivity is not a constant;-   the sensitivity depends at least on the liquid volume to be detected    and/or on the wetted area (possibly also on other parameters);-   preferably a different sensitivity or sensitivity curve is    predefined depending on liquid volume and/or the wetted area;-   preferably the classification into sensitivity classes is made    according to the intensity of the capacitance jump during immersion    or emergence of the sensor;-   a suitable threshold value, a suitable series of threshold values or    a suitable threshold value function is predefined by means of the    sensitivity class;-   a different series of threshold values or a different threshold    value function is applied depending on the sensitivity class of the    liquid (i.e. depending on the conductivity and permittivity).

The precise presetting of the sensitivity for a liquid to be measured isparticularly important since capacitive liquid level measurements (cLLD)are very sensitive. An incorrect setting can lead to incorrect or veryinaccurate results. The invention offers a higher reliability in cLLD asa result of the automated classification.

For successful capacitive liquid level measurements (cLLD), theselection or specification of a suitable sensitivity setting istherefore made possible according to the invention, preferably in allembodiments. Preferably the specification of a suitable sensitivitysetting is carried automatically by the device in all embodiments.

It is an advantage of the invention that the user of a device need notbe concerned about detailed information of the liquids which are to beused. In addition, he preferably need not make any manual inputs in anyof the embodiments since the device of the invention is designed toautomatically classify one or more liquids, e.g. after retrieving acorresponding procedure and/or to predefine the presetting(s) for asubsequent capacitive liquid level measurement (cLLD).

The invention in all embodiments makes the configuration sequence andthe handling of such devices simpler and less liable to error.

The invention, depending on implementation, enables a more intelligentdetection and reaction to errors when carrying out a capacitive liquidlevel measurement (cLLD).

The invention enables the mechanical and physical limits of present-dayliquid handling systems to be further advanced and go to the smallestvolumes.

The capacitive liquid level measurement (cLLD) of the inventionfunctions with any current labware (container) such as microplates withwells, plastic or glass tubes and trays.

Preferably in all embodiments special carriers are used for receiving orcarrying the labware (containers) which are optimized for a capacitiveliquid level measurement (cLLD). Such a carrier should fulfil one ormore of the following criteria:

-   the carrier walls are designed to be non-conductive;-   the carrier base is designed to be conductive and earthed (for    example, together with the worktable);-   the carrier base is designed so that it is located near the liquid.

The invention preferably in all embodiments carries out a capacitiveliquid level measurement (cLLD) with evaluation of a fast and a slowsignal, where different threshold values are used to evaluate the fastsignal and for the slow signal. In this case, at least one of the twothreshold values (preferably both threshold values) has a dependence onthe liquid volume that is to be detected and/or a dependence on the areawetted instantaneously by the liquid to be measured.

The physical properties of a liquid need not be known in any embodimentof the invention.

The invention in all embodiments offers a higher reliability of thecapacitive liquid level measurement (cLLD) as a result of the automatedclassification carried out previously according to the invention.

The invention enables a more intelligent detection and reaction toerrors.

With the invention it is possible to detect smaller volumes within theframework of the capacitive liquid level measurement (cLLD) thanpreviously (e.g. up to about 2 μl tap water in a well with a V-shapedbase of a 384-well microplate).

With the invention it is also possible to detect smaller volumes withinthe framework of the capacitive liquid level measurement (cLLD) ofpoorly conducting liquids (e.g. up to about 30 μl ethanol in a well witha V-shaped base of a 384-well microplate).

In all embodiments, in most cases a single cLLD detection is sufficient,i.e. a measurement need not be repeated. This applies particularly if,as mentioned, one fast and one slow signal is used in the capacitiveliquid level measurement (cLLD).

The handling systems (devices) according to the invention and themethods according to the invention are now explained in detail by meansof schematic drawings of exemplary embodiments which do not restrict thescope of the invention.

FIG. 1 shows a schematic view of a laboratory apparatus according to theprior art;

FIG. 2 shows a schematic graph with the results of measurementsaccording to the invention of four different liquids in an EppendorfTube®;

FIG. 3 shows a schematic flow diagram of a first exemplary method of theinvention;

FIG. 4A shows a schematic view of a first device according to theinvention which on the one hand is designed for carrying out acapacitive measurement and classification of a liquid and on the otherhand for carrying out a capacitive liquid level measurement (cLLD);

FIG. 4B shows a schematic view of a part of another device according tothe invention which comprises an earthed worktable on which a carrierwith 8 tubes is disposed;

FIG. 4C shows a perspective view of an exemplary carrier which is herefitted with 12 tubes;

FIG. 5 shows a schematic intensity-time diagram in which two signalsaccording to the invention of a capacitive liquid level measurement(cLLD) are presented in simplified form in order to be able to describethe application of two different threshold values (and possibly othercriteria) according to a further embodiment;

FIG. 6A shows a schematic view of three identical containers which areeach filled with different liquid volumes;

FIG. 6B shows a schematic diagram which is related to the three fillinglevel situations shown in FIG. 6A, where on the one hand the signalintensity is shown on emergence of the sensor from a conductive liquidand on the other hand suitable threshold values;

FIG. 7 shows a schematic diagram which shows a series of discretethreshold values which are suitable for carrying out a capacitive liquidlevel measurement (cLLD) which evaluates a first faster and a secondslower signal;

FIG. 8A shows a highly schematic diagram which is related to a containershown on the left where a curve is predefined for each of three liquidclasses in the diagram;

FIG. 8B shows a highly schematic diagram which is related to a containershown on the left where a curve is predefined for each of three liquidclasses in the diagram.

Exemplary liquid handling systems 100 are described hereinafter, wherethe invention can however easily also be applied to other handlingsystems, laboratory systems, medical and pharmaceutical systems and thelike. These systems are designated overall here as devices 100.

The term container 101 (also called labware) comprises inter alia thefollowing containers: microplates with wells, trays, tubes (made ofglass or plastic), containers, bottles, flasks and the like.

In addition, each container 101 is assigned a carrier 103.1 (here alsocalled carrier 103.1) on which or in which the container 101 can bedisposed, as shown in schematic form in FIGS. 4A, 4B and 4C by referenceto several examples.

When in the following there is talk of a type of sensor 102, a type ofcontainer 101, a type of carrier 103.1 or a type of worktable 103.2, theword “type” should then comprise the geometry and the material.

The carrier 103.1 is located above a worktable 103.2 or another suitablesurface as can be seen for example in FIG. 4B.

The worktable 103.2 together with the carrier 103.1 is here designatedas container environment 103.

In order to enable a reliable and repeatedly accurate determination ofthe liquid level by means of capacitive liquid level measurement cLLD,the liquids 1 to be measured are divided into different sensitivitygroups or classes. This process is here also designated asclassification (or grouping) of a liquid 1. This classification ispreferably carried out in all embodiments by means of the direct orindirect measurement of the conductivity and effective staticpermittivity of the respective liquid 1.

Investigations have revealed that within the framework of the inventionno absolute measurement or determination of the conductivity and thepermittivity are required. A qualitative assessment of the liquids 1 issufficient for all embodiments.

The conductivity and permittivity are specific material properties whichare used here indirectly for classifying liquids 1 by means of acapacitive measuring process (called capacitive measurement) whichoperates in a summarizing (integrating) manner.

The permittivity of matter, here of a liquid 1, (usually specified as s)designates the dielectric conductivity of the matter. The unit istypically As/Vm. The permittivity is frequency-dependent. It is, forexample, very strongly defined in water.

The permittivity can also be represented as a product of thefrequency-dependent permittivity ε(ω) (also called relative dielectricconstant) and the field constant ε₀ (dielectric constant of vacuum).

The specific magnitude of the conductivity for a predefined geometry ofa measuring arrangement is linked via the admittance Y to the complexfrequency-dependent impedance. The conductivity can therefore berecorded directly by measurement techniques in a device 100 of theinvention.

“Siemens/μm” (S/μm) is used as the unit for the conductivity. Example:highly pure water has 0.05 μS/cm to 0.1 μS/cm and tap water has 300μS/cm to 1 mS/cm.

Preferably in all embodiments a capacitive measurement is carried out(see step S1 in FIG. 3) in order to then relate the liquid 1 or comparedwith predefined (e.g. with previously determined) reference quantities,which can be provided, for example, from a memory 107 (see FIG. 4A).

The classification is made in all embodiments by means of a capacitivemeasurement (see step S1 in FIG. 3). Preferably this capacitivemeasurement is made during immersion or emergence of a sensor 102.However, a capacitive measurement can also be carried out whilst thesensor 102 is located in the liquid 1. In the latter case, an absolutemeasurement is made in order to be able to classify the liquid 1.

Within the framework of the invention, preferably in all embodiments thesame capacitive liquid level measurement system 110 which is also usedsubsequently for detecting the liquid level is used to determine thesensitivity group or class or to classify the liquids 1.

Preferably in all devices 100 therefore one and the same liquid levelmeasurement system 110 is used both for classifying liquids 1 and alsofor detecting the liquid level. This has the advantage that the resultsof the automated classification can be readily transferred and appliedto the capacitive liquid level measurement.

Preferably in all embodiments a special classification module 104 isused which enables an influencing or adjustment of the (measurement)sensitivity of a charging/discharging circuit 2 and/or a signalprocessing circuit 6 via a circuitry-wise connection or link 106, asindicated in FIG. 4A.

According to the embodiment, the classification module 104 can predefinethe threshold values corresponding to the circuits 2 and/or 6, thresholdvalue series or a threshold value function sV(FV) or sV(bO) or it can,for example, trigger the specification of a threshold value, a series ofthreshold values or a threshold value function sV(FV) or sV(bO) by meansof a signal or a quantity e.

The functional groups or assemblies of FIG. 4A can be partially or allcombined together in one circuit where such a circuit is preferably aprocessor-controlled circuit which comprises at least one processorwhich processes instructions/commands from a memory.

In this case and in other embodiments which comprise a processor, thereis talk here of a processor-based implementation. Such an implementationcomprises a combination of hardware and software.

Within the framework of the invention preferably in all embodimentsfrequency-dependent conduction processes are measured in the liquidsystem to be investigated by capacitive methods. This process is heredesignated as capacitive measurement (step S1 in FIG. 3). Compared witha resistance measurement of the liquid 1 using a direct current, thecapacitive measurement of the impedance yields a substantially moreinformative complex quantity Z or the jump of a complex quantity Z. Theembodiments of the invention are therefore based on a capacitivemeasurement which uses an alternating voltage (AC voltage). In allembodiments of the invention, this alternating voltage can be provided,for example, by a charging/discharging circuit 2 and applied to thesensor 102. The sensor 102 is in this case charged with a low potential.During immersion into or emergence from the liquid 1, an abrupt changein the capacitance is obtained which can be measured or evaluated (e.g.by the circuit 104 or 6).

When performing the capacitive measurement, the measurement orevaluation is accomplished, for example, by the classification module104. When performing the capacitive liquid level measurement, themeasurement or evaluation is made, for example, by the signal processingcircuit 6. However, both can also be made in a common circuit module.

An ideal sensor geometry for characterizing the material properties of aliquid 1 comprises a homogeneous electric field in the liquid 1 to bestudied with negligible edge effects and stray field capacitances. Thisrequirement is only fulfilled by two plane-parallel electrode plates ofinfinite extension between which the liquid 1 is disposed. In a realdevice 100 the environment is significantly different. Investigationshave shown that by means of a linearly deliverable sensor 102 in thereal environment of a container 101, sufficiently accuratedeterminations can be made within the framework of a capacitivemeasurement to enable a classification. In particular, it has been shownthat such capacitive measurements are sufficient in order to classifythe liquids 1 to be studied into one of several (preferably three)sensitivity groups or classes.

Compared to dielectrics, liquids exhibit a very complex behaviour in thesolid phase. In the liquid phase various charge transport processes aswell as reversible and irreversible electrochemical reactions can occurdepending on frequency and amplitude of an acting electric alternatingfield and the temperature. Thus, within the framework of the invention afrequency band of 200 kHz to 500 kHz and preferably of 250 kHz to 350kHz is selected for the capacitive measurement in order to avoidelectrochemical reactions in the liquid 1 to be studied as far aspossible.

Preferably in all embodiments the same frequency band is used in theautomated classification as in the capacitive liquid level measurementcLLD. Thus, preferably the same circuit 2 can be used in both processes.

The amplitude of the alternating voltage (AC voltage) to be applied tothe sensor 102 is obtained from the requirement for a suitably largesignal-to-noise ratio. Preferably in all embodiments of the invention,the applied alternating voltage has a charge curve which ends at about 5V depending on the sensor geometry used.

Preferably in all embodiments the same amplitude is used in theautomated classification as in the capacitive liquid level measurement.Thus, preferably the same circuit 2 can be used in both processes.

Preferably in all embodiments the same direct voltage fraction(polarization voltage) is used in the automated classification as in thecapacitive liquid level measurement. The direct voltage fraction(polarization fraction) is preferably about 3 V.

The procedure for determining the sensitivity group or class or forclassifying a liquid 1 preferably comprises the following steps:

-   providing a (defined) liquid volume FV of the liquid 1 to be    classified. This is preferably accomplished in all embodiments in a    defined container 101, i.e. in a container 101 of previously    specified type.-   A (defined) sensor 102, preferably a sensor 102 of previously    specified type, is delivered into the (defined) liquid volume FV of    this liquid 1 (called immersion movement) and a capacitive    measurement of the liquid 1 is performed (in this case) with a    previously suitably adapted sensitivity or with the maximum    sensitivity. In this case, preferably in all embodiments a defined    measurement environment is used. Such a defined measurement    environment preferably comprises at least one defined container 101    (here also designated as dedicated container) and a defined carrier    103.1.-   By means of a (detection) signal s(t), which is provided by the    sensor 102 during the capacitive measurement of the liquid 1, the    liquid 1 is classified into one of several sensitivity groups or    classes. Preferably all the embodiments use a signal jump of the    (detection) signal s(t) or the intensity of the (detection) signal    s(t) of the capacitive measurement in order to perform the    classification into a sensitivity group or class. Preferably in all    embodiments the classification into a sensitivity class is made by    relating the intensity of the (detection) signal s(t) to at least    one predefined threshold value. If the intensity of the (detection)    signal s(t) lies above the predefined threshold value, this liquid    is classified into a first sensitivity class (step S4 in FIG. 3). If    the intensity of the (detection) signal s(t) lies below the    predefined threshold value, this liquid is classified into a second    sensitivity class (step S5 in FIG. 3).-   The classification of the liquid 1 thus made into a specific    sensitivity group or class is then used (immediately or    subsequently) in a capacitive liquid level measurement cLLD in order    to predefine the suitable sensitivity (pre)setting for this liquid    level measurement.

The capacitive measurement of the liquid 1 is preferably made in allembodiments by the device 100 performing the capacitive measurement withthe highest sensitivity. By means of the signal intensity measured withthe highest sensitivity and the predefined threshold values, the liquidis classified into one of several sensitivity groups or classes.

Preferably the capacitive measurement of the liquid 1 is performedsuccessively in the same tube 101 using, for example, all eight sensorsof a laboratory apparatus 100 provided with pipette tips of the sametype 102 (e.g. a 200 disposable tip 102 can be used eight times). Thefirst of the eight measurements is preferably discarded since it isfrequently falsified by electrostatic effects. From the remaining sevenmeasurements preferably in all embodiments the median of the measuredsignals is determined and the classification is performed on the basisof this median.

FIG. 4A shows that a classification module 104 is connectedcircuitry-wise to the charging/discharging circuit 2 in order to connectthe automated classification to the execution of the capacitive liquidlevel measurement.

In all embodiments the classification module 104 can however also beonly connected circuitry-wise to the signal processing circuit 6 or toboth circuits 2 and 6.

According to the invention, the classification of a liquid 1 into aspecific sensitivity group or class also enables a capacitive liquidlevel measurement cLLD to be made in a different environment (e.g. in adifferent container 101 or in a different platform or device 100).

By means of the specific sensitivity group or class, a computationaladaptation can be made to a different liquid volume FV and/or to adifferent wetted area and/or to a different container 101 and/or to adifferent carrier 103.1 and/or to a different worktable 103.2 and/or toa different pipette tip 102. In this case the device 100 comprises amodule or the device 100 can be connected to a module which performs acomputational adaptation before one of the two circuits 2, 6 or bothcircuits 2, 6 are then set or reset accordingly for a liquid levelmeasurement cLLD.

Preferably all the embodiments are designed so that they are capable ofidentifying or eliminating liquids 1 which are not suitable for acapacitive liquid level measurement in the device 100. Theidentification or elimination can be made, for example, if thecapacitive measurement of a liquid 1 gives a (detection) signal s(T)which does not allow any classification because, for example, it liesbelow a minimum value (lower threshold value).

FIG. 2 shows a graphical diagram of measurements which were conductedusing four different liquids in a device 100 of the invention. Each ofthe four liquids is assigned a different graphical signal as shown inthe legend to FIG. 2. The first liquid here comprises EtOH (ethanol),the second liquid comprises diwater (distilled and de-ionized water),the third liquid comprises tap water and the fourth liquid comprises3-molar NaCl (sodium chloride).

FIG. 2 reveals that the first and second liquids can be clearlydistinguished if the (signal) intensity SI of the (detection) signals(t) is examined. The third and fourth liquids can be distinguished lessclearly by an examination of the intensity SI, where in each case thesethird and fourth liquids can in turn be clearly distinguished from thefirst and second liquids. Here so-called volume units VE are plotted onthe x axis (e.g. in 10 μl steps).

FIG. 3 shows a schematic diagram of a preferred method 200 of theinvention. The method 200 is divided in the exemplary embodiment showninto five steps which are characterized by S1 to S5.

In the first step S1 a capacitive measurement of a liquid 1 is made.This capacitive measurement can be carried out when executing animmersion movement of the sensor 102 into the liquid 1 or when executingan emerging movement of the sensor 102 from the liquid 1. The capacitivemeasurement yields a (detection) signal s(t) which is preferablyprocessed in all embodiments by a separate or integrated classificationmodule 104 (see FIG. 4A).

Preferably in all embodiments within the framework of step S2, a signaljump of a signal s(t) of the capacitive measurement which is obtainedduring the immersion movement of the sensor 102 into the liquid 1 orduring the emerging movement of the sensor 102 from the liquid 1 isprocessed or examined in order to perform the automated classificationof the liquid 1.

In the second step S2, for example, the intensity (signal strength) ofthe (detection) signal s(t) in the area of the signal jump isexamined/determined and in step S3 a classification or grouping isperformed by means of a predefined threshold value (e.g. sV1) which inthe example shown here lies at −60. In the diagram in FIG. 2, no unitfor the intensity SI was intentionally predefined since this unitdepends on the specific circuitry-wise implementation. In a similarcircuitry-wise arrangement the signal intensity SI can be given e.g. inmV. In a digital circuitry-wise arrangement, the signal intensity SI canbe given, for example, in ADU. ADU stands for analog-digital conversionand designates the number of quantification steps which were used toquantify the analog (detection) signal s(t).

In FIG. 2 the point cloud of the first liquid lies in the range between−50 and −18 whereas the point cloud of the second liquid lies in therange between −90 and −70. A threshold value sV1 was predefined as −60.This threshold value (e.g. sV1) is interrogated in step S3. If themeasured intensity of the (detection) signal s(t) lies above −60, thecorresponding liquid is classified into the first sensitivity class(called 1st Cl.). Otherwise the liquid is classified into a secondsensitivity class (called 2nd Cl.). Another threshold value could bespecified, e.g. at −100. Now, another step could be added, for example,to step S3 which checks whether the measured intensity of the(detection) signal s(t) is less than −100. If this is the case, it canthen be ascertained, for example, that this liquid is not suitable for acapacitive liquid level detection in the device 100.

Accurate investigations show that there can be various factors whichhave an influence on the classification of the liquids. If suchinfluences are present, these are taken into account according to theinvention when performing the measurements and/or when evaluating themeasurements. Among others, the following (environmental) influences canplay a role:

-   the liquid volume FV of the liquid 1 in the container 101,-   type of container 101 (material and geometry),-   type of sensor 102 (material and geometry),-   type of carrier 103.1 (material and geometry),-   type of worktable 103.2 (material and geometry).

The instantaneously wetted surface area can be determined in each casefrom the instantaneous liquid volume FV of the liquid 1 in the container101 and from the geometry of the container 101, if necessary. Orconversely the sensitivity can have a dependence on a curve or series ofvalues which is related to the wetted surface area, i.e. in such a casethere is a dependence of the threshold value Sv(bO) on the wettedsurface area.

In addition, the wiring e.g. of the carrier 103.1 and of the worktable103.2 plays a role. Through earthing, for example, they can both be atthe same potential, which is advantageous. FIG. 4B shows a schematicexample, in which a container 101 with a round base rests in a carrier103.1 which sits on a worktable 103.2. The worktable 103.2 and/or thecarrier 103.1 can be earthed. Preferably in all embodiments theworktable 103.2 is earthed (as shown in FIG. 4B) and the carrier 103.1comprises a non-conducting material (e.g. plastic). An earthed containerenvironment 103 is particularly suitable.

The automated classification of the liquid 1 can be accomplished in allembodiments of the invention in a predefined classification environmentof the device 100. Such a predefined classification environment ischaracterized in that at least one of the following specifications isidentical to the specifications (determination environment) which areused when determining the predefined threshold values (e.g. T1):

-   the liquid volume FV of the liquid 1 in the container 101 or the    wetted surface area between the liquid 1 and the container 101,-   the type of sensor 102,-   the type of container 101 (preferably a dedicated container is    used),-   the type of carrier 103.1,-   the type of worktable 103.2, on which the (dedicated) carrier 103.1    is disposed.

If the wetted surface area between the liquid 1 and the container 101 isknown, the type of container 101 and the liquid volume FV need notnecessarily be known since the wetted surface area is dependent on thetype of container 101 and on the liquid volume FV.

The present invention makes it possible to classify or distinguish e.g.containers 101, when the capacitive measurements are made with a known(predefined) liquid, a known (predefined) liquid volume FV and a known(predefined) sensor 102 in an otherwise known environment 103. In thiscase, a classification or distinction, e.g. of the containers 101 can bemade, for example, by means of the intensity of the signal s(t). Thus,for example, (cLLD) suitable containers 101 could be automaticallydistinguished from unsuitable ones.

Preferably all embodiments of the device 100 are equipped with automatedmeasurement procedures which are designed to classify or distinguish

-   containers 101 and/or-   carriers 103.1 and/or-   worktables 103.2 and/or-   sensors 102.    In this case, in a device 100 which is equipped with a corresponding    measurement procedure, it is, for example, possible to determine in    which type of container 101 a liquid 1 is located or, for example,    which type of sensor 102 (which sensor type) is used currently.

The present invention also makes it possible to distinguish betweenvarious liquids 1 which are (should be) used in the device 100 if thesedifferent liquids 1 can be distinguished by means of their permittivityand conductivity. Such a distinction between different liquids 1 can bemade without the previously described classification. For such adistinction it is merely sufficient to make a comparative capacitivemeasurement, i.e. it is sufficient in this case if relative measurementsare made. If it is known, for example, that in a device 100 only ethanolis present as first liquid and distilled de-ionized water is present assecond liquid, these two liquids can be distinguished by means of anintensity examination of the signals s(t). In this way, confusions ofliquids 1 can be avoided in an automated sequence.

Preferably all embodiments are equipped with a measurement procedurewhich is suitable for distinguishing different liquids 1.

Influences which can be produced by spatial inhomogeneities of thetemperature, the pressure and the liquid concentration or by aperturbing field are not considered here. In order to achieve a highreproducibility however, as far as possible the essential aspects whichcan have an influence should be specified.

Preferably in all embodiments, the determination of a liquid-specificvalue is made. This liquid-specific value can be derived, for example,by means of the intensity of the signal s(t) (e.g. obtained by a tableenquiry from a table or determined by circuitry) or it can be calculatedor derived from the intensity of the signal s(t). This liquid-specificvalue, if present, preferably in all embodiments can be used for theprecise setting of the threshold value(s) for the subsequent capacitiveliquid level measurement cLLD in the device 100. In this case, theliquid-specific value(s) are made available to the circuit 2 and/or 6before carrying out a capacitive liquid level measurement cLLD. Thecircuit 2 and/or 6 is then automatically preset to a suitablesensitivity (e.g. E1 or E2) by predefining the threshold value(s) forthe capacitive liquid level measurement cLLD.

Depending on the embodiment, the presetting of the sensitivity can bemade by specifying one or more threshold values sV1, sV2 or a thresholdvalue function sV(FV) or sV(bO) by the circuit 2 and/or 6 or thepresetting can be made by a signal or a control variable which istransmitted or provided by the classification module 104 via aconnection 106 to the circuit 2 and/or 6, as shown in FIG. 4A. In FIG.4A it is indicated that the circuit 2 can comprise an influenceableswitch or an actuator 12 which can be switched/converted directly orindirectly by the signal or the control variable.

If (only) a classification of the liquid 1 into a class has been made,as shown for example in FIG. 3, the setting of the threshold value(s)for a subsequent capacitive liquid level measurement cLLD in the device100 can be made by means of the assignation to a specific class. Eachsuch class can then be assigned, for example, a constant threshold value(e.g. sV1). If therefore, for example, in a liquid 1 in the device 100 aliquid level measurement cLLD is to be made, the assignation of theliquid 1 to a specific class is examined in order to make the setting ofthe threshold value(s) according to this class.

Preferably the device 100 of the invention comprises a (changeover)switch or an actuator 12 (as already mentioned) in order toautomatically set the suitable threshold values before a liquid levelmeasurement cLLD is made. The set threshold values can be constant.Preferably in all embodiments they have a dependence on the liquidvolume FV (therefore designated as sV(FV)) or they have a dependence onthe wetted surface area (therefore designated as sV(bO).

FIG. 4A shows an exemplary implementation of a device 100 whichaccording to the invention is equipped with an already mentioned module104, which is designed for automated classification of a liquid 1 withinthe device 100. The module 104 can, as shown in FIG. 4 a, be connecteddirectly to the sensor 102 via a line connection 105. If a capacitivemeasurement (step S1 in FIG. 3) is performed, the module 104 determines,for example, the intensity of the signal s(t) which was tapped at thesensor 102 (e.g. during execution of an immersion movement) or otherproperties of a signal jump. Then, for example, the liquid 1 located inthe container 101, is classified into one of two different sensitivityclasses. If now at a later time point in the device 100 a liquid levelmeasurement cLLD of the liquid 1 is to be performed in the container 101(or in another container), the module 104 influences the setting of thethreshold value(s) of the charging/discharging circuit 2 (and/or of thecircuit 6). FIG. 4A shows an embodiment in which a (changeover) switchor an actuator 12 enables the switchover from a first sensitivity E1 toa second sensitivity E2 (or conversely). The higher the sensitivity, thelower the corresponding threshold value is set and conversely.

According to the invention, in all embodiments of the invention thesensitivity can be predefined (depending on the previously accomplishedclassification of the liquid 1),

-   in order to be able to predefine the corresponding signals (e.g. the    amplitude of the alternating voltage and/or the frequency) during    charging/discharging of the sensor 102 by the charging/discharging    circuit 2 and/or-   in order to make a corresponding setting of the sensitivity (e.g. by    adapting an amplification factor in the circuit 6) when    evaluating/processing the signal a(t) (e.g. by the circuit 6).

In this way a “usable” (e.g. a signal having few perturbing influences)output signal a(t) of a liquid level measurement cLLD by thecharging/discharging circuit 2 is provided which can be furtherprocessed and evaluated in a subsequent signal processing circuit 6.

The sequence of the process 200 can, for example, be triggered and/ormonitored by the controller 7 of the device 100. The module 104 canhowever also have its own controller (processor) for the sequencecontrol of the process 200.

Both when executing the capacitive measurement and also during a liquidlevel measurement cLLD the signal which can be tapped at the sensor 102during immersion and during emergence makes a signal jump. Duringimmersion the signal has a different sign to that during emergence.Preferably during the automated classification of a liquid 1 and alsowhen executing a liquid level measurement cLLD the jump height or theamplitude is evaluated. Here therefore there is talk of the signalintensity SI of the signal s(t) in the range of the signal jump.

As already mentioned, the automated classification of the liquid 1preferably in all embodiments is made with the aid of desired valueswhich (e.g. in a predefined determination environment of the device 100)were determined and then stored (e.g. in a memory 107, see FIG. 4A).Since desired values can be used for assistance, the invention operateswith qualitative or relative predictions. If, for example, the signaljump is greater than sV1=−60, the corresponding liquid 1 is classifiedinto first class, etc.

In all embodiments within the framework of the capacitive measurement afaster signal s1(t) and a slower signal s2(t) can be derived/obtainedfrom the (detection) signal and processed. From these two signals s1(t)and s2(t) a first threshold value sV1 for the fast signal s1(t) and asecond threshold value 5W for the slow signal s2(t) are determined. Thisprocedure is optional.

FIG. 5 now show a liquid level measurement cLLD which is based on theprocessing of a faster signal s1(t) and a slower signal s2(t). In FIG. 5the behaviour of the signal intensity SI of the two signals is plottedover the time t. In addition, the position of the two threshold valuesvSs and vSl is shown. If the signal s1(t) exceeds the first thresholdvalue vSs, this can be seen as a first positive indication for theimmersion or emergence (depending on the sign). Now if the signal s2(t)exceeds the second threshold value vSl (here with vSl>vSs), this can beseen as definitive confirmation for the immersion or emergence(depending on sign).

In practical applications, in addition to these two threshold valuesvSs, vSl preferably other criteria (here the pulse width P1 of the firstsignal s1(t) and the slope ST of the second signal s2(t)) are evaluatedto check the correctness of the detection.

According to the invention, during the automated classification of theliquid 1 at least two different threshold values vSs, vSl and preferablyother criteria (P1, ST) can be determined and stored for a subsequentuse in a liquid level measurement cLLD. The threshold values vSs, vSl inpreferred embodiments have a dependence on the liquid volume FV and/oron the wetted surface area.

In all embodiments for a subsequent liquid level measurement cLLD withfast signal s1(t) and slow signal s2(t) the threshold values vSl of theslow signal s2(t) can be determined from the threshold values vSs of thefast signal S1(t) or conversely.

Embodiments are described hereinafter in which the threshold value(s)are not constant. These embodiments are based on the finding that thereis a dependence on the liquid volume FV of the liquid 1 to be classifiedand/or the wetted surface area. Precise investigations of the variousdependences in which the following aspects also have an influence haveshown that the intensity SI has a special curve profile.

The intensity SI is strongly dependent on the following aspects:

-   conductivity and relative static permittivity of the liquid 1 as    already mentioned;-   liquid volume FV and the type of container 101 and/or on the wetted    surface area;-   type of carrier 103.1;-   type of sensor 102;-   type of worktable 103.2;-   materials of the elements mentioned;-   speed of the movement B.

In a liquid level measurement cLLD according to the invention, the jumpof the signal a(t) or the signal intensity SI must be significantlygreater than all these perturbing influences.

For conductive liquids 1 the signal s(t) or a(t) becomes increasinglysmaller closer to the base of the container 101, the smaller the volumeFV becomes or the smaller the instantaneously wetted surface areabecomes.

The shape (geometry) of the container 101 is also relevant. For example,for the same liquid volume FV the signal intensity SI is higher in acontainer 101 having a slightly curved base (see, e.g. FIG. 4B) than ina container having a V-shaped base (see, e.g. FIG. 8B).

According to the invention even the smallest volumes should be mademeasurable/detectable. That is, the limits of the feasible should beshifted in the direction of small volumes FV. Preferably volumes FVwhich are smaller than 10 μl and preferably smaller than 5 μl should bedetectable.

In order to achieve good results in a capacitive liquid levelmeasurement cLLD according to the invention, in all embodiments thematerial of the container 101 should be non-conductive and the base ofthe container 101 can contact the earthed worktable 103.2 or be closethereto (distance AB<2 mm, see FIG. 4B).

Preferably in all embodiments, special carriers 103.1 are used which areoptimized for a capacitive liquid level measurement cLLD. Such a carrier103.1 should fulfil one or more of the following criteria (reference ismade here to the example of FIG. 4B):

-   the carrier walls 103.3 are designed to be non-conductive;-   the carrier base 103.4 is designed to be conductive and earthed (for    example, together with the worktable 103.2 as shown schematically in    FIG. 4B);-   the carrier base 103.4 is designed so that it is located close to    the liquid 1.

FIG. 4C shows a perspective view of an exemplary carrier 103.1 which ishere fitted with 12 tubes 101. In this diagram the base 103.4 of thecarrier 103.1 and the walls 103.3 can be clearly seen. The carrier base103.4 can for example be connected to the working area 103.2 so that itis earthed together with the working area 103.2.

All in all, the following rules or approaches should be taken intoaccount if particularly reliably and precisely operating devices 100 orprocesses 200 are to be provided.

-   The threshold value is related to the jump in the capacitance    (signal jump) which occurs during immersion (or emergence).-   The threshold value must be balanced between the sensitivity with    respect to the liquid 1 and the lack of sensitivity with respect to    the environment (e.g. the container environment 103).-   If the threshold value is set too low, the liquid level measurement    cLLD becomes increasingly sensitive. As a result, incorrect    measurements become more probable.-   If the threshold value is set too high, the liquid level measurement    cLLD becomes increasingly insensitive. That is, the sensor 102 must    be inserted more deeply into the liquid 1 (missing of a liquid    level) before the capacitance jump is sufficiently large to be able    to be detected. In addition, liquids 1 with weak conductivity can    then no longer be detected.

FIG. 6A shows a schematic view of three identical containers 101 whichare each filled with different liquid volumes FV. The liquid volume FVdecreases from left to right. FIG. 6B shows a schematic diagram which isrelated to the three fill level situations shown in FIG. 6A. Thisdiagram shows on the one hand the signal intensity SI during emergenceof the sensor 102 from a conducting liquid 1 and on the other handsuitable threshold values.

Some of the statements already made above can be confirmed from thesefigures. The intensity SI decreases as the liquid volume FV becomessmaller or with decreasing wetted surface area. The intensity curve(upper curve in FIG. 6B) has a distinct first region M1 which ismonotonically decreasing and which can be approximated by a straightline having a constant gradient. The intensity curve also has a secondregion M2 which is strongly decreasing and whose gradient increases. Nomeasurement results are available for very small volumes FV.

According to the invention, preferably in all embodiments within theframework of the automated classification, each value of the intensitycurve is assigned a corresponding threshold value. In order that signalsremain detectable during immersion or emergence in a liquid levelmeasurement cLLD, the associated threshold value must always be slightlylower than the values of the intensity curve. In FIG. 6B the lower curverepresents a possible profile of a threshold value curve.

According to the invention, preferably in all embodiments a series ofdiscrete threshold values is determined (as shown, e.g. in FIG. 7). Inall embodiments however a threshold value function sV(FV) or sV(bO) canbe determined where the threshold value function sV(FV) has a dependenceon the liquid volume FV or the threshold value function sV(bO) has adependence on the wetted surface area of the liquid 1 in the container101.

Preferably in all embodiments the liquid level measurement cLLD isperformed so that the liquid volume FV to be measured and/or theinstantaneous wetted surface area have/has an influence on the choice ofthe threshold value. With decreasing liquid volume FV or with decreasingwetted surface area, the threshold value preferably also decreases.Consequently the sensitivity of the cLLD liquid level measurementbecomes increasingly lower.

FIG. 7 shows a schematic diagram which shows a series of discretethreshold values which are suitable for performing a capacitive liquidlevel measurement cLLD which evaluates a first faster signal s1(t) and asecond slower signal s2(t) (see also FIG. 5). The volume units areplotted on the x axis and the signal intensity SI is plotted on the yaxis. With increasing volume FV the signal jump during immersion oremergence becomes increasingly greater, i.e. the intensity SI increases.Accordingly the threshold values also become increasingly larger.

Preferably in all embodiments which operate with two signals s1(t),s2(t) threshold value curves are used whose profile for both signals isidentical or similar (as shown in FIG. 7). The threshold value curve forthe faster signal s1(t) is designated by vSs and the threshold valuecurve for the slower signal s2(t) is designated with vSl. Preferably inall embodiments it holds that vSl>vSs (as also shown in FIG. 5).

FIG. 8A shows a highly schematic diagram which is related to a container101 shown on the left, which here has a slightly curved base 108. Inthis diagram a curve 201, 202, 203 is predefined for each of threeliquid classes which are shown in schematic form in FIG. 8A. In thediagram the volume unit VE is plotted as a function of the sensitivity.It can also be seen here that for the liquids of all three sensitivityclasses 1st Cl., 2nd Cl. and 3rd Cl., the sensitivity must decreasesignificantly with decreasing volume FV (or with decreasing wettedsurface area) in order to be able to perform successful liquid levelmeasurements cLLD. The three curves 201, 202, 203 can be the same orsimilar, as shown in FIG. 8A. However, the three curves can also besignificantly different, as shown in FIG. 8B.

FIG. 8B shows a highly schematic diagram which is related to a container101 shown on the left, which here has a V-shaped tapering base 108. TheV-shaped base 108 is particularly clearly defined here in order to showa situation in which the dependence of the curve profiles on the wettedsurface area can be clearly identified. As in FIG. 8A the threesensitivity classes 1st Cl., 2nd Cl. and 3rd Cl. are shown. For a liquidhaving particularly good conductivity (3rd Cl.), the corresponding curve204 has a monotonically slightly increasing profile (which, for example,in the region M1 can be linearly ascending). In the region of thetransition from the purely cylindrical region of the container 101 tothe tapering base 108, the curve 204 has a curved profile with clearlyincreasing slope (region M2 in FIG. 8B). The curve 205 of the goodconducting liquid (2nd Cl.) has a rectilinear profile which has no slopeand no gradient or whose slope or gradient is very small (region M1 inFIG. 8B). For the curve 206 of the poorly conducting liquid (1st Cl.)the curve 206 tilts towards the right in the schematic diagram of FIG.8B. This curve 206 has a rectilinear profile with a gradient in theregion M<2 in FIG. 8B. The tilting of the curve 206 to the right canexplained in a simplified manner in that for a poorly conducting liquidthe size of the wetted area in the region M1 of the curve 206 does notplay any role. In this region the distance AB from the worktable 103.2is significantly more dominant. [000143] It can be deduced from FIG. 8Bthat the sensitivity curves of various liquids can certainly have adifferent profile. Therefore the threshold value curves can also have adifferent profile according to the conductivity of the liquid.

Preferably two and particularly preferably three sensitivity classes 1stCl., 2nd Cl., and 3rd Cl., can be predefined (see also FIG. 8A and 8B).These sensitivity classes 1st Cl., 2nd Cl., and 3rd Cl. can be definedas follows, for example:

-   Conductive liquids having a conductivity <10 μS and relative static    permittivity between 24 and 80 (poor conductivity: 1st Cl.)-   Conductive liquids with conductivity <10 μS and relative static    permittivity >80 (good conductivity 2nd Cl.)-   Conductive liquids with conductivity >100 μS (very good conductivity    3rd Cl.).

REFERENCE LIST

Liquid 1 Charging/discharging circuit 2 Pipette tip 3 Base plate 4Container 5 Signal processing circuit 6 Controller 7 Laboratoryapparatus 10 Input side 11 Switch/actuator 12 Device 100 Container(Labware) 101 Sensor 102 Carrier/support 103.1 Worktable/surface/baseplate 103.2 Carrier wall 103.3 Carrier base 103.4 Container environment103 Classification module 104 Line connection 105 Circuitry connection106 Memory 107 Base 108 Liquid level measurement system 110 Method 200Curves 201, 202 , 203, 204, 205, 206 Output signal of cLLD a(t) DistanceAB Delivery movement B Liquid level measurement cLLD Capacitance betweensensor and liquid C_(tip/liq) Series capacitance C_(coupl) Permittivityε Frequency-dependent permittivity ε(ω) Field constant ε₀ Controlvariable or signal e First sensitivity E1 Second sensitivity E2 Liquidvolume FV Process steps S1, S2, S3, S4, S5, S6 Output signal/(detection)signal s(t) (Signal) intensity SI Sensitivity class Kl First range M1Second range M2 Time t First threshold value sV1 Second threshold valuesV2 Threshold value function as a function sV(FV) of liquid volumeThreshold value function as a function sV(bO) of wetted surface areaVolume units VE Predefined threshold value vS Predefined threshold valuefast signal vSs Predefined threshold value slow signal vSl Admittance YComplex quantity/impedance Z

1. Method (200) for executing a capacitive liquid level measurement(cLLD) of a liquid (1) in a container (101), wherein the method (200)comprises the following steps: providing the liquid (1) in a container(101), executing the capacitive liquid level measurement (cLLD) whenexecuting an immersion movement of a sensor (102) into the liquid (1) orwhen executing an emerging movement of a sensor (102) from the liquid,wherein before or during execution of the immersion movement or theemerging movement a sensitivity adaptation of the capacitive liquidlevel measurement (cLLD) is made by means of a series of predefineddiscrete threshold values (vS1; vS2) or by means of a predefinedthreshold value function (vS(FV); vS(bO)) and the discrete thresholdvalues (vS1; vS2) or the threshold value function (vS(FV); vS(bO)) havea dependence on the liquid volume (FV) of the liquid (1) in thecontainer (101) and/or on the wetted surface area.
 2. Method accordingto claim 1, wherein the capacitive measurement (200) for the automatedclassification of the liquid is performed in a device (100) andcomprises the following steps: providing the liquid (1) in a container(101), providing a line connection 105 between a classification module104 and a sensor 102, which can be operated at different sensitivitiesperforming a capacitive measurement of this liquid (1) when executing animmersion movement of the sensor (102) into the liquid (1) or whenexecuting an emerging movement of the sensor (102) out from the liquid(1), wherein a signal jump of a signal (s(t)) of the capacitivemeasurement is processed which is formed during the immersion movementof the sensor (102) into the liquid (1) or during the emerging movementof the sensor (102) from the liquid (1) in order to perform theautomated classification of the liquid (1)
 3. The method according toclaim 2, characterized in that the intensity (SI) of the signal (s(t))in the region of the signal jump and/or the amplitude of the signal jumpare processed in order to perform the automated classification of theliquid (1).
 4. The method (200) according to claim 2, characterized inthat the following steps are executed for the automated classificationof the liquid (1): classification (S4) of the liquid (1) into a firstsensitivity class if the signal jump of the signal (s(t)) of thecapacitive measurement lies above a predefined threshold value (vS),classification (S5) of the liquid (1) into a second sensitivity class ifthe signal jump of the signal (s(t)) of the capacitive measurement liesbelow the predefined threshold value (vS).
 5. The method (200) accordingto claim 2, characterized in that the automated classification of theliquid (1) is made with the aid of desired values which were determinedin a predefined determination environment of the device (100) and thenstored.
 6. The method (200) according to claim 5, characterized in thatthe automated classification of the liquid (1) is accomplished in adefined classification environment of the device (100), wherein theclassification environment is identical to the determination environmentat least with reference to one of the following specifications: theliquid volume (FV) of the liquid (1) in the container (101), surfacearea wetted by the liquid (1) in the container (101), the type of sensor(102), the type of container (101), the type of carrier (103.1) for thecontainer (101), the type of worktable (103.2) on which the carrier(103.1) is disposed.
 7. The method (200) according to claim 2,characterized in that a dedicated sample container serves as container(101) which is filled with a known liquid volume (FV) of the liquid (1),wherein a processor-controlled procedure for automated determination ofthe sensitivity of this liquid (1) is executed for automatedclassification of the liquid (1).
 8. The method (200) according to claim7, characterized in that within the framework of this procedure thesensor (102) is immersed from a position above a level of the liquid (1)in the dedicated sample container into the liquid (1), wherein duringimmersion of the sensor (102) the capacitive measurement (cLLD) isexecuted and wherein by means of a capacitance change which is obtainedduring immersion either a sensitivity value is determined for thisliquid (1) or the liquid (1) is classified into a sensitivity class bymeans of a comparison with predefined quantities.
 9. The method (200)according to claim 2, characterized in that within the framework of thecapacitive measurement a plurality of sensors (102) consecutivelyexecute an immersion movement into the container (101), wherein duringimmersion of a first sensor (102) a first signal jump or a firstintensity value and during immersion of a second sensor (102) a secondsignal jump or a second intensity value are determined and wherein anaverage value is formed from the two signal jumps or the two intensityvalues.
 10. The method (200) according to claim 2, characterized in thatin a subsequent step in the device (100) a capacitive liquid levelmeasurement (cLLD) is performed using a signal (s(t); s1(t), s2(t))which is provided by the sensor (102) wherein for this capacitive liquidlevel measurement (cLLD) an adjustment of the sensitivity (E1, E2) ofthe capacitive liquid level measurement (cLLD) is automatically made bymeans of the previously accomplished classification.
 11. The method(200) according to claim 4, characterized in that the automatedclassification of the liquid (1) is made with the aid of desired valueswhich were determined in a predefined determination environment of thedevice (100) and then stored.
 12. The method (200) according to claim 4,characterized in that the dedicated sample container serves as container(101) which is filled with a known liquid volume (FV) of the liquid (1),wherein a processor-controlled procedure for automated determination ofthe sensitivity of this liquid (1) is executed for automatedclassification of the liquid (1).
 13. The method (200) according toclaim 6, characterized in that the dedicated sample container serves ascontainer (101) which is filled with a known liquid volume (FV) of theliquid (1), wherein a processor-controlled procedure for automateddetermination of the sensitivity of this liquid (1) is executed forautomated classification of the liquid (1).
 14. The method (200)according to claim 4, characterized in that within the framework of thecapacitive measurement a plurality of sensors (102) consecutivelyexecute an immersion movement into the container (101), wherein duringimmersion of a first sensor (102) a first signal jump or a firstintensity value and during immersion of a second sensor (102) a secondsignal jump or a second intensity value are determined and wherein anaverage value is formed from the two signal jumps or the two intensityvalues.
 15. The method (200) according to claim 6, characterized in thatwithin the framework of the capacitive measurement a plurality ofsensors (102) consecutively execute an immersion movement into thecontainer (101), wherein during immersion of a first sensor (102) afirst signal jump or a first intensity value and during immersion of asecond sensor (102) a second signal jump or a second intensity value aredetermined and wherein an average value is formed from the two signaljumps or the two intensity values.
 16. The method (200) according toclaim 4, characterized in that within the framework of the capacitivemeasurement for the liquid (1) a threshold value (vS1; vS2) and/or aseries of discrete threshold values (vS1; vS2) and/or a threshold valuefunction (vS(FV); vS(bO)) is/are determined, wherein the threshold valuefunction (vS(V); vS(bO)) has a dependence on the liquid volume (FV) ofthe liquid (1) in the container (101) or on the wetted surface area inthe container (101).
 17. The method (200) according to claim 6,characterized in that within the framework of the capacitive measurementfor the liquid (1) a threshold value (vS1; vS2) and/or a series ofdiscrete threshold values (vS1; vS2) and/or a threshold value function(vS(FV); vS(bO)) is/are determined, wherein the threshold value function(vS(V); vS(bO)) has a dependence on the liquid volume (FV) of the liquid(1) in the container (101) or on the wetted surface area in thecontainer (101).
 18. The method (200) according to claim 4,characterized in that in a subsequent step in the device (100) acapacitive liquid level measurement (cLLD) is performed using a signal(s(t); s1(t), s2(t)) which is provided by the sensor (102) wherein forthis capacitive liquid level measurement (cLLD) an adjustment of thesensitivity (E1, E2) of the capacitive liquid level measurement (cLLD)is automatically made by means of the previously accomplishedclassification.
 19. The method (200) according to claim 6, characterizedin that in a subsequent step in the device (100) a capacitive liquidlevel measurement (cLLD) is performed using a signal (s(t); s1(t),s2(t)) which is provided by the sensor (102) wherein for this capacitiveliquid level measurement (cLLD) an adjustment of the sensitivity (E1,E2) of the capacitive liquid level measurement (cLLD) is automaticallymade by means of the previously accomplished classification.